Soft magnetic materials usually have low coercive force and narrow hysteresis loop. Soft magnetic materials are of main importance for modern electrical engineering and electronics and are indispensable for many devices and applications. Here we introduce some of the popular materials as below.
The main purpose of adding silicon to iron is to reduce the conductivity of iron and in that way to reduce the eddy-current loss in the alloy. The second beneﬁcial effect of alloying iron with silicon is reducing magnetostriction and, thus, reducing the acoustic noise caused by cyclic stresses resulting from magnetostriction strains in AC applications. For XIANYU products, one important application of silicon steel is zero-phase current transformers.
Permalloy is the nickel-iron alloys consisting of 36%~81% nickel. The applications of iron-nickel alloys are in the transformers and inductor cores at audio frequencies. Some of the high permeability alloys with relative permeability up to 300,000 are used for magnetic screening. But one of the drawbacks of permalloy is the high price, as nickel is an expensive material.
The most important characteristic of ferrites, as compared to other magnetic materials, is the high volume resistivity of the material. In high-frequency applications eddy current losses are usually dominant and increase approximately with the square of the frequency. These losses are inversely proportional to the resistivity. Therefore the high resistivity of the ferrites is the factor most contributing to their wide application in high-frequency magnetic components.
The general chemical formula is XFe2O3, where X represents one or more divalent transition metals, such as manganese, zinc, nickel, cobalt, or magnesium. The most common combinations are manganese and zinc (MnZn) or nickel and zinc (NiZn). Due to the low manufacturing cost, the ferrite cores are still widely used.
Amorphous soft magnetic materials are alloys of iron and other magnetic or transition metals such as cobalt, nickel, boron, silicon, niobium, and manganese.
Amorphous materials exhibit linear hysteresis loops with low coercivity and a saturation induction of 0.7–1.8 T. The values of the saturation induction are almost completely retained at high frequency. The Curie temperature of the amorphous materials is in the range of 350–450C. Amorphous materials can be used for split cores or act as the DC immune CT core together with nanocrystalline.
The advantages of iron-based nanocrystalline materials lie in the high values of the saturation induction, the reduction of volume of the magnetic components, the low heat dissipation, and the stable operation up to 120C.
Nanocrystalline soft magnetic materials exhibit a linear hysteresis loop with coercivities smaller than 2 A/m and a saturation induction of 1.2–1.5 T. The initial permeability of the material is adjustable in the range of 15,000 to 150,000. Nanocrystalline cores have applications of many different areas, such as switched-mode power supplies, precision current transformers, commom-mode chokes and so on.